UBS said Tuesday that it swung sharply to profit in the fourth quarter as Switzerland's biggest bank pushes ahead with a bid to operate in slimmed-down form.

Zurich-based UBS, which was severely hit by the financial crisis six years ago and has since struggled to fashion its scandal-prone investment bank into a reliable supplement to its flagship wealth management business, said the results reflect the "flexibility" of its new model.

UBS has been shedding assets, trimming its balance sheet and curbing riskier or more exotic trades at its investment bank as it strives for what it calls a "capital-light" model.

It posted fourth-quarter net profit of Sfr917 million ($1 billion) compared with a loss of roughly Sfr1.9 billion a year earlier. The bank's core wealth management business drew in net new money of Sfr5.8 billion, more than twice the amount in the same period a year earlier.

UBS's investment bank swung to a pretax operating profit of Sfr297 million, compared with a loss of Sfr243 million in the period a year earlier. The investment bank reported 62 billion francs in risk-weighted assets, below UBS' self-imposed limit of Sfr70 billion for the business.

In October, UBS gave investors an unpleasant surprise by disclosing it had been hit with a mandatory addition to its balance sheet courtesy of Switzerland's financial regulator. The bank said the regulator, Finma, required UBS to stock up on some Sfr28 billion in operational risk-related assets to protect it from matters such as "unknown" future litigation.

The requirement spurred the bank to say that it would likely no longer be able to reach its goal of a 15% return on equity by 2015. However, on Tuesday UBS said that following a subsequent review by Finma, the requirement has since been reduced by about Sfr5 billion.